The reasons people hate Jews are varied. Hate is learned. If their parents or culture enforces that hate, it will continue. There are some groups that have historically targeted and hated Jews. It is sad, and we need to move beyond this in modern society.

Perhaps it is because the Jews are one of the only religions that is also a nationality. You can be many kinds of Catholic, and you can, of course, convert to Judaism, but in most cases the Jewish religion entails being a nationality. There has always been "competition" among nationalities (which I was younger it was the Irish and the Italians in my neighborhood, although it wasn't all that intense :)).

I think the same confusion exists with Muslims today. Many Arabs happen to be Muslim, but I think it's radical groups that are causing many of the problems because they are radicals, not because they are Muslims. They may use the faith as a cover for their actions, but I think the real issue is political philosophy and that religion is only a convenient vehicle.

There is also the unfortunate historical perception of the Jews as "Christ Killers," arms dealers to the world, and usurious money lenders (cf. "The Merchant of Venice").

The hatred is not because of the religion. The hatred is because of the prejudice and bias that has evolved and developed in the hater. In addition, people who hate, are not happy inside themselves. They might say, "I like myself," but if they're haters they usually don't. One exception would be for sociopaths who have no moral responsibility or social conscience.

Since the diaspora to the various parts of Europe (and even before that, truly) Jews have been discriminated against. Some would even say it has become part of their identity - enduring the hardships of discrimination. They were easy targets in Europe. They had different customs, tended to intermarry in the religion, were successful (something to be envied and/or blamed) and mostly segregated. Pogroms, anti-Semitic riots, became commonplace in Europe throughout the modern age.

Unfortunately, this happens all of the time, to various groups of people. People often "hate" other groups of people just because they are different. Like the previous post mentioned, religion has a lot to do with discrimination towards Jewish people. It really just boils down to differences in opinions and stereotyping.

There have been various reasons why people have hated Jews over the years, and we have no way of knowing which one motivates any given person, at least not based just on them saying "I hate Jews." The two main reasons have been:

Religion. Christians historically hated Jews based on the idea that they were the ones who were responsible for killing Jesus Christ.

Separatism. Jews have been forced to live separately from gentiles and have often, therefore, been seen as these secretive people who keep to themselves and scorn others. They were also often quite rich compared to their neighbors. This has led many people to hate Jews not exactly for religious reasons but for more economic and cultural reasons tied to the fact that the Jews did not mingle and assimilate.